Cryptosporidiosis is caused by the protozoan parasite Cryptosporidium parvum (C. parvum). Historically, C. parvum had been recognized as a cause of diarrhea and mortality in young animals with an undeveloped immune system. It was not until the outbreak of acquired immunodeficiency syndrome (AIDS) that C. parvum was considered a significant problem in humans (Petersen, "Cryptosporidiosis in patients infected with the human immunodeficiency virus," Clinical Infectious Diseases, 15:903-909, 1992). Increased awareness and improved diagnostic techniques indicate that C. parvum may now be one of the three most important enteropathogens causing diarrheal illness worldwide (Laughon, et al., "Summary of the workshop on future directions in discovery and development of therapeutic agents for opportunistic infections associated with AIDS," The Journal of Infectious Diseases, 164:244-251, 1991). Pediatric outbreaks have been reported in hospitals (Navarrete, et al., "An outbreak of Cryptosporidium diarrhea in a pediatric hospital," The Pediatric Infectious Disease Journal, 10:248-250, 1991) and day care centers (Anonymous, "Cryptosporidiosis among children attending day-care centers--Georgia, Pennsylvania, Michigan, California, New Mexico," Morbid. Mortal. 33:599-601, 1984). Even more recently, a large waterborne outbreak in Milwaukee, Wisconsin affected more than 400,000 persons (MacKenzie, et al., "A massive outbreak in Milwaukee of Cryptosporidium infection transmitted through the public water supply," New England Journal of Medicine, 331:161-167, 1994).
C. parvum infection is acquired by the ingestion of oocysts which persist in the environment from the feces of infected animals or humans. During the life cycle of C. parvum numerous oocysts may be produced which may be excreted into the environment or remain within the host for autoinfection (Fayer, and Ungar, "Cryptosporidium spp. and cryptosporidiosis," Microbiological Reviews, 50:458-483, 1986). Oocysts are remarkably resistant to most common disinfectants, and routine chlorination of drinking water most likely has no effect on their viability (Current, "The biology of Cryptosporidium," ASM News, 54:605-611, 1988). This environmentally resistant oocyst aids in the organisms transmission through either contamination of the water supply or individual-individual contact. Some researches suggest that as few as 30 oocysts are required to infect an individual, but in the case of an immunosuppressed individual 1 oocyst may be sufficient. This may be supported by the fact that only 8 to 10 oocysts per 100 liters of water were found in the recent outbreak in Milwaukee (Schwartz, et al., "Biliary cryptosporidiosis in HIV+ patients after a waterborne outbreak in Milwaukee," Gastroenterology, 106(4):A770 (abstr), 1994). Interestingly, our government recently issued the following tap-water warning: "Federal health officials have warned the nation that the daily threat of cryptosporidiosis is so widespread that anyone with a weakened immune system might want to avoid drinking water straight from the tap. The U.S. Environmental Protection Agency and Centers for Disease Control and Prevention said that people with severely weakened immune systems should take precautions such as boiling water, installing filters or using bottled water. Those at risk are people with AIDS or HIV; cancer patients; transplant patients; people with genetically weakened immune systems; and malnourished children." (The Columbus Dispatch Saturday, Jun. 17, 1995 Page 4A). To date no therapy has proven to be clinically efficacious.
Although cryptosporidiosis can be problematic for any person, its most notable impact has been among patients with human immunodeficiency virus (HIV). Clinical features include chronic (cholera-like) diarrhea, abdominal cramps, fatigue, weight loss, etc. In immunocompetent persons the onset of this disease is explosive but generally self-limiting in about two weeks. However, this condition is very debilitating to the immunosuppressed individual and is life-threatening. Recently, Blanshard and Gazzard ("Natural history and prognosis of diarrhoea of unknown cause in patients with acquired immunodeficiency syndrome (AIDS)," Gut, 36:283-286, 1995) have shown that C. parvum-associated diarrhea in AIDS patients is correlated with a significantly shorter median survival time. In their study the median survival time for patients with "pathogen negative" diarrhea was 48.7 months, which was similar to that of control patients with no diarrhea; however, median survival time was significantly longer than that of matched patients with a gastrointestinal pathogen (9.6 months). Of those patients with pathogen positive diarrhea, about 40% were determined to be caused by C. parvum. Others have documented the higher mortality rate in AIDS patients with cryptosporidiosis compared to noninfected AIDS patients (Gilson, et al., "Impact of a community-wide outbreak of cryptosporidiosis on patients with AIDS," Tenth International Conference of AIDS, 2:24 (abstr), 1994).
The true prevalence of cryptosporidiosis is not known. It has been estimated that 10 to 20 percent of AIDS patients in the U.S. have developed chronic C. parvum diarrhea, while the incidence is probably greater in developing countries where contaminated water supplies are of greater concern. Reported incidence rates are an underestimate of the occurrence of C. parvum infection because of its past unrecognized pathogenicity in humans and relative difficulty to identify.
Although numerous therapies have recently been tested, none appear to improve this debilitating condition. There is disclosed herein a method of reducing intestinal infestation by C. parvum by daily enteral supplementation with probiotics. Probiotics have been defined as a live microbial feed supplement which beneficially affects the host by improving its intestinal microbial balance (Fuller, "Probiotics in man and animals," Journal of Applied Bacteriology, 66:365-378, 1989). Some researchers believe that this normalization of the intestinal microbiota will confer the following benefits: (a) protection against pathogens by competitive exclusion (also termed colonization resistance); (b) provision of certain nutrients and enzymatic/detoxification reactions; (c) involvement in tissue morphogenesis and peristaltic activity; and (d) interaction with the immune and endocrine systems of the host (Speck, et al., "Lactobacillus reuteri in food supplementation," Food Technology, July:90-94, 1993). Examples of probiotic organisms include several lactic acid bacteria such as the lactobacilli, streptococci, and bifidobacteria.
The more common intestinally found lactobacilli in healthy persons are Lactobacillus reuteri (L. reuteri) and Lactobacillus acidophilus (L. acidophilus). L. reuteri is an ubiquitous organism of man and animals. Of the intestinal lactic acid bacteria (LAB), L. reuteri is considered one of the most dominating species. Due to the inability of microbiologists to distinguish L. reuteri from Lactobacillus fermentum (L. fermentum) in the past, many researchers believe that a large percentage of LAB classified as L. fermentum in older literature, in reality, are strains of L. reuteri.
L. reuteri is a typical heterofermentative Lactobacillus species. Like other lactobacilli, L. reuteri produces acidic metabolic end-products (acetate and lactate) which have considerable antimicrobial activity. It has been recently discovered that metabolism of glycerol by L. reuteri can result in excretion of a metabolic intermediate, 3-hydroxypropionaldehyde (reuterin; Axelsson, "Production of a broad spectrum antimicrobial substance by Lactobacillus reuteri," Microbial Ecology in Health and Disease, 2:131-136, 1989). This compound has been shown to have antimicrobial activity against a variety of organisms to include Gram-positive and Gram-negative bacteria, yeast, molds and protozoa (Chung, et al., "In vitro studies on reuterin synthesis by Lactobacillus reuteri," Microbial Ecology in Health and Disease, 2:137-144, 1989). It is suspected that the antimicrobial activity of reuterin contributes to the survival of L. reuteri within the gastrointestinal ecosystem.
Likewise, L. acidophilus is a normal inhabitant of the human gastrointestinal tract. L. acidophilus is a homofermentative species, fermenting mainly hexose sugars, yielding predominantly lactic acid (85-95%). The use of L. acidophilus dates back to the early 20th century.
There is provided in accordance with one aspect of the present invention a method of inhibiting the infection of a mammal by Cryptosporidium parvum by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection.
There is provided in accordance with another aspect of the present invention a method of inhibiting the infection of a mammal by Cryptosporidium parvum by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection as evidenced by a reduction in the shedding of Cryptosporidium parvum oocysts in the feces.
There is provided in accordance with another aspect of the present invention a method of inhibiting the infection of the intestine of a mammal by the oocysts of Cryptosporidium parvum by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection.
There is provided in accordance with another aspect of the present invention a method of inhibiting the infection of the intestine of a mammal by the oocysts of Cryptosporidium parvum by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection as evidenced by a reduction in the shedding of Cryptosporidium parvum oocysts in the feces.
There is provided in accordance with another aspect of the present invention a method of increasing the resistance to Cryptosporidium parvum infection in an immunocompromised mammal by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection.
There is provided in accordance with another aspect of the present invention a method of increasing the resistance to Cryptosporidium parvum infection in an immunocompromised mammal by enterally administering Lactobacillus reuteri in an amount which is therapeutically effective to inhibit said infection as evidenced by a reduction in the shedding of Cryptosporidium parvum oocysts in the feces.